1. Field of the Invention
The present invention relates generally to coating apparatus and, more particularly to a method and apparatus for coating industrial cutting and turning tools and the like so as to improve the tools' working properties.
2. The Prior Art
Industrial society requires, among others, the use of lathe, milling and other industrial cutting and turning machines for the production of many goods. These machines in turn require hard-edged tooling. Such tooling must exhibit an acceptable cutting rate and a minimum useful life. Improvements in cutting rate and useful life of such tooling lead to improved productivity, hence lower manufacturing costs.
Initial efforts were directed at improving the composition of the materials from which the tools were shaped. These included, among others, the various high speed and hot-work steels and tungsten carbides. These initial efforts were followed by further enhancing the desired properties of these advanced materials by providing the tools formed from such materials by some sort of a coating. Depending on application, such coatings have included aluminum-oxide and titanium-nitride coatings for tungsten-carbide and diamondlike carbon coatings for hard alloy HG 10, steel and aluminum. See "Preparation of Hard Coatings by Ion Beam Methods," by C. Weissmantel et al, Thin Solid Films, 63 (1979) pp. 315-325.
More recently, cubic boron nitride (CBN) has received a great deal of attention as a most desired coating for such industrial tooling. This is so since CBN is the second hardest material known, just after diamond. CBN is comparable to diamond in hardness, compressive strength and in wear and abrasion resistance, and also is chemically inert at high temperatures. These qualities have made CBN into a promising material for forming such cutting and turning tools. See "Sythesis of Polycrystalline Cubic BN," by M. Wakatsuk, et al, Mat. Res. Bull., Vol. 7, pp. 999-1004 (1972). CBN is, however, difficult to make. It requires high pressures and high temperatures. Although the ion beam deposition of CBN coatings onto hard alloy substrates recently has been investigated (see "Ion Beam Deposition of Special Film Structures," by C. Weissmantel, J. Vac. Sci. Technol., 18(2), March 1981, and "Structure and Properties of Quasi-Amorphous Films Prepared by Ion Beam Techniques," by C. Weissmantel et al, Thin Solid Films, 72 (1980) pp. 19-31), the only known commercial method to coat industrial cutting and turning tools with CBN is the one developed by the General Electric Company. This GE commercial method also is based on high pressure and high temperature technology, and requires extensive processing. Consequently, CBN coated tools are very expensive. Further, the GE method can only coat tooling parts of relatively simple shape and configuration, its application is thus further restricted.